We have not done any testing on these units as we are just vendors for the product. You should be able to find reviews for the LINK-S on Youtube, in firearms/hunting forums online and through Facebook, and direct from Spypoint, the manufacturer.
The Spypoint LINK-S Cellular Trail Camera requires an SD card up to 32 GB to store information. If the SD card is full, no further pictures or videos can be stored.
The SIM card is "Preactivated" per Spypoint. Here is set up and general information from Spypoint regarding the LINK-S units:
https://www.youtube.com/watch?v=yjeU8U67wxQ
If you are having bad connectivity I would recommend reaching out to Spypoint to see what recommendations they have to possibly strengthen the signal. Here is their contact information:
https://www.spypoint.com/en/support
The SIM card is "Preactivated" per Spypoint. Here is set up and general information from Spypoint regarding the LINK-S units:
https://www.youtube.com/watch?v=yjeU8U67wxQ
There is nothing in the manual to suggest that another camera can be paired wirelessly to share the cellular of this unit.
Mark H.